American society in the 18th century became more complex because of population growth, increasing ethnic diversity (particularly in the central and southern Anglo-American colonies), the expansion of urban centers and an urban elite, the development of internal trade and consumption of goods. The increasing ehtnic diversity made American society more complex because it introduced new traditions and new religious creeds. The formation of an urban elite led to social and economic differentiation within American society.
These urban elite were also particularly receptive to the major current of thought of the era, the Enlightenment, which stressed the power of reason over superstition and religious dogmas in guiding human behavior. In opposition to the Enlightenment, which represented a clear break with the beliefs of the previous century, the Great Awakening was a religious revival of the 1740s that sought to reconnect American society with the Calvinism that was one of the founding values of 17th century.
The 18th century was also the century of the American Revolution which made society more complex dividing it along political lines and leading to independence from Great Britain.